4.3BSD hostname case insensitivity

[Joseph S. D. Yao]

In article <762 at mips.UUCP> dce at mips.UUCP (David Elliott) writes:
>We have had customer complaints saying that they need to be able to
>have case-sensitivity in hostnames.
>Is there any reason that one of the following could not be done?
>	1. Allow case-sensitivity in hostnames ...
>	2. Change the routines to understand either case. That is, have
>	   hostname "MyHoSt" be the same as "myhost".
>Is there a definitive document ...

Apologies if this has already been answered; we lost news for a while.

In the ARPA research community, papers are forever working papers,
and are called "Requests for Comments" (RFC's) -- and, indeed, may
in fact be modified long after they are published.  The reference
you seek is RFC#822: Standard for the Format of ARPA Internet Text
Messages.  This isn't the only such document (ISO is working on one,
for instance), but it's been around a long time ... and it's the one
of which I have a copy.  And the one on which sendmail is (however
loosely) based.

3.4.7  CASE INDEPENDENCE
   Except as noted, alphabetic strings may be represented in any
   combination of upper and lower case.  The only syntactic units
   which requires [sic] preservation of case information are:
	- text	- qtext	- dtext	- ctext	- quoted-pair
	- local-part, except "Postmaster"
   When matching any other syntactic unit, case is to be ignored.
   For example, the field-names "From", "FROM", "from", and even
   "FroM" are semantically equal and should all be treated ident-
   ically.

   When generating these units, any mix of upper and lower case
   alphabetic characters may be used.  The case shown in this
   specification is suggested for message-creating processes.

   Note:  The reserved local-part address unit, "Postmaster", is
	  an exception.  When the value "Postmaster" is being
	  interpreted, it must be accepted in any mixture of
	  case, including "POSTMASTER", and "postmaster".  [sic]

In other words, only local mailbox names (lognames & group aliases),
the body of the message, and text that's somehow protected are re-
quired to have case information preserved.  That is for the benefit
of primitive operating systems which work better with only one case
(no flames!  I said it to be funny, ha-ha!).  Sendmail, purely for
its own convenience in interpreting these things, takes this quite
literally when translating things to LC for comparisons and not
retaining the cased versions.  Other mailers (MMDF, perhaps?) might
retain case info in the delivered version.

However, your customers are in violation of standards if they claim
to need case in host names.
-- 

	Joe Yao		hadron!jsdy at seismo.{CSS.GOV,ARPA,UUCP}
			jsdy at hadron.COM (not yet domainised)